Print foundation positioning and printing methods for additive manufacturing system

ABSTRACT

Method for printing a three-dimensional part layerwise with an additive manufacturing system includes printing layers by depositing material from a print head onto a print foundation, incrementing a position of the print head relative to the print foundation after each layer is printed, and indexing the print foundation carrying the printed layers away from the print head along the printing axis after a number of layers are printed. Printing is performed with driven and fixed rails clamped against movement of the print foundation. Moving the print foundation includes moving the driven rails with respect to the fixed rails in a direction substantially perpendicular to the build plane. Additive manufacturing system includes a drive mechanism to index the print foundation on the printing axis using fixed and driven rails, the driven rails engaging the print foundation for moving the print foundation.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/248,982, entitled “PRINT FOUNDATION POSITIONINGAND PRINTING METHODS FOR ADDITIVE MANUFACTURING SYSTEM” filed on Oct.30, 2015, the contents of which are incorporated herein by reference inits entirety. Reference is also hereby made to co-filed U.S. PatentApplication Ser. No. 62/248,990, entitled “STARTER PIECE AND PRINTINGMETHODS FOR ADDITIVE MANUFACTURING SYSTEM” and U.S. Patent ApplicationSer. No. 62/248,994, entitled “PROBE AND PRINTING METHODS FOR ADDITIVEMANUFACTURING SYSTEM”. Each of the patent applications and patentsdiscussed herein is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to additive manufacturing systems forbuilding three-dimensional (3D) items with layer-based, additivemanufacturing techniques. In particular, the present disclosure relatesto additive manufacturing systems for printing large or elongated 3Ditems, and methods for printing 3D items in the additive manufacturingsystems.

Additive manufacturing systems are used to print or otherwise build 3Ditems from digital representations of the 3D items (e.g., AMF and STLformat files) using one or more additive manufacturing techniques.Examples of commercially available additive manufacturing techniquesinclude extrusion-based techniques, jetting, selective laser sintering,powder/binder jetting, electron-beam melting, and stereolithographicprocesses. For each of these techniques, the digital representation ofthe 3D item is initially sliced into multiple horizontal layers. Foreach sliced layer, one or more tool paths are then generated, whichprovides instructions for the particular additive manufacturing systemto print the given layer.

For example, in an extrusion-based additive manufacturing system, a 3Ditem may be printed from a digital representation of the 3D item in alayer-by-layer manner by extruding a flowable item material. The itemmaterial is extruded through an extrusion tip or nozzle carried by aprint head of the system, and is deposited as a sequence of roads on asubstrate in an x-y plane while the print head moves along the toolpaths. The extruded item material fuses to previously deposited itemmaterial, and solidifies upon a drop in temperature. The position of theprint head relative to the substrate is then incremented along a z-axis(perpendicular to the x-y plane), and the process is then repeated toform a 3D item resembling the digital representation.

In fabricating 3D items by depositing layers of an item material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of 3D items under construction,which are not supported by the item material itself. A support structuremay be built utilizing the same deposition techniques by which the itemmaterial is deposited. The host computer generates additional geometryacting as a support structure for the overhanging or free-space segmentsof the 3D item being formed. Support material is then deposited from asecond nozzle pursuant to the generated geometry during the printingprocess. The support material adheres to the item material duringfabrication, and is removable from the completed 3D item when theprinting process is complete.

SUMMARY

An aspect of the present disclosure is directed to a layerwise methodfor printing a three-dimensional part with an additive manufacturingsystem. The method includes printing a plurality of layers of thethree-dimensional item by depositing material from a print head onto aprint foundation of the additive manufacturing system, incrementing aposition of the print head relative to the print foundation after eachlayer is printed, and indexing the print foundation carrying the layersaway from the print head along the printing axis after printing aplurality of layers of the three-dimensional item in a directionsubstantially perpendicular to the build plane. Printing is performed inone aspect with a plurality of driven and fixed rails configured toclamp the three-dimensional item against movement independent of theprint foundation. Moving the print foundation includes moving the drivenrails with respect to the fixed rails in the direction substantiallyperpendicular to the build plane.

Another aspect of the present disclosure is directed to an additivemanufacturing system including a print foundation, and a drive mechanismconfigured to index the print foundation along a printing axis, thedrive mechanism comprising a gantry having a frame with a plurality ofsupport rails and a drive system configured to move the print foundationalong the gantry. The drive system further includes a rail system havinga plurality of fixed rails and a plurality of driven rails, the drivenrails configured to engage the print foundation for moving the printfoundation.

Another aspect of the present disclosure is directed to a method forprinting a three-dimensional item with an additive manufacturing system.The method includes supplying a starter piece and a print foundation forprinting of the three-dimensional item, printing a plurality of layersof a support structure on the starter piece and a plurality of layers ofthe three-dimensional item on the print foundation, and indexing theprint foundation along a gantry with a drive mechanism, wherein printingis performed with a plurality of driven and fixed rails each having aclamp releasably clampable to the three-dimensional item, and whereinindexing the print foundation includes moving the driven rails withrespect to the fixed rails after a plurality of layers are printed.

DEFINITIONS

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The terms “about” and “substantially” are used herein with respect tomeasurable values and ranges due to expected variations known to thoseskilled in the art (e.g., limitations and variabilities inmeasurements).

The term “printing onto”, such as for “printing a 3D item onto a printfoundation” includes direct and indirect printings onto the printfoundation. A “direct printing” involves depositing a flowable materialdirectly onto the print foundation to form a layer that adheres to theprint foundation. In comparison, an “indirect printing” involvesdepositing a flowable material onto intermediate layers that aredirectly printed onto the receiving surface. As such, printing a 3D itemonto a print foundation may include (i) a situation in which the 3D itemis directly printed onto to the print foundation, (ii) a situation inwhich the 3D item is directly printed onto intermediate layer(s) (e.g.,of a support structure), where the intermediate layer(s) are directlyprinted onto the print foundation, and (iii) a combination of situations(i) and (ii).

The term “providing”, such as for “providing a chamber” and the like,when recited in the claims, is not intended to require any particulardelivery or receipt of the provided item. Rather, the term “providing”is merely used to recite items that will be referred to in subsequentelements of the claim(s), for purposes of clarity and ease ofreadability.

The term “item” includes, by way of example only and not by limitation,standalone printed structures or parts that are utilized in combinationwith other parts to form a desired structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of an additive manufacturingsystem according to an embodiment of the present disclosure.

FIG. 2 is a perspective view of a platen and gantry portion of theadditive manufacturing system of FIG. 1.

FIG. 3 is a top view of FIG. 2.

FIG. 4 is a perspective view of a portion of an additive manufacturingsystem illustrating an item movement system according to an embodimentof the present disclosure.

FIG. 5 is a top view of the portion of the additive manufacturing systemof FIG. 4.

FIG. 6 is a perspective view of a drive system for an additivemanufacturing system according to another embodiment of the presentdisclosure.

FIG. 7 is a perspective view of a drive rail and platen according to anembodiment of the present disclosure.

FIG. 8 is a close-up perspective view of a portion of a platen and drivesystem according to an embodiment of the present disclosure.

FIG. 9 is a perspective view of a starter piece according to anembodiment of the present disclosure.

FIG. 10 is a top view of the starter piece of FIG. 9.

FIG. 11 is a rear elevation view of the starter piece of FIG. 9.

FIG. 12 is a perspective view of another starter piece according to anembodiment of the present disclosure.

FIG. 13 is a rear elevation view of the starter piece of FIG. 12.

FIG. 14 is a perspective view of starter pieces in place on an additivemanufacturing system according to an embodiment of the presentdisclosure, with parts of the system removed to show detail thereof.

FIG. 15 is a perspective view of a portion of an additive manufacturingsystem according to an embodiment of the present disclosure, showingstarter pieces, a platen, and a portion of a drive system.

FIG. 16 is a close-up perspective view of a portion of an additivemanufacturing system according to an embodiment of the presentdisclosure, showing starter pieces, a platen, and a portion of a drivesystem.

FIG. 17 is a perspective view of a fiducial according to anotherembodiment of the present disclosure.

FIG. 18 is a close-up view of the fiducial of FIG. 17.

FIG. 19 is a flow chart of a method according to an embodiment of thepresent disclosure.

FIG. 20 is a perspective view of a purge system according to anembodiment of the present disclosure

FIG. 21 is a side elevation view of the purge system of FIG. 20 in a Zdetection position.

FIG. 22 is a side elevation view of the purge system of FIG. 20 in an XY detection position.

FIG. 23 is a close-up perspective view of a portion of the purge system.

FIG. 24 is a perspective view of a portion of an additive manufacturingsystem according to another embodiment of the present disclosure.

FIG. 25 is a perspective view of the additive manufacturing system ofclaim 29 with a print foundation removed.

FIG. 26 is a close-up perspective view of a portion of an additivemanufacturing system with a limit switch assembly according to anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to an additive manufacturing systemhaving an extended printing volume for printing long or tall 3D items.The additive manufacturing system includes a drive system for indexing aprint foundation along a gantry or other support as the item is beingprinted. The additive manufacturing system includes in one embodiment aheated chamber having a port that opens the chamber to ambientconditions outside of the chamber. The system also includes one or moreprint heads configured to print a 3D item in a layer-by-layer manneronto a print foundation (e.g., a platen or other component having areceiving surface, which may be a build sheet fixed on a vacuum platen)in the heated chamber. As the printed 3D item grows on the printfoundation, the print foundation may be indexed or otherwise movedthrough the port by the drive system in a coarse indexing adjustment.The print head may also be indexed to the layers of thethree-dimensional item in a fine indexing adjustment. The printed 3Ditem may continue to grow out of the port until a desired length orheight is achieved. The use of the port expands the printable volumealong a printing axis of the system, allowing long or tall 3D items,such as airfoils, manifolds, fuselages, and the like to be printed in asingle printing operation. As such, the 3D items may be larger than thedimensions of the additive manufacturing system, for example itemshaving a length greater than a length of the build chamber.

The present disclosure is further directed to a touch probe for use withan additive manufacturing system having an extended printing volume forprinting long or tall 3D items, methods for printing and for operatingthe additive manufacturing system with the touch probe, and methods forprinting and operating the additive manufacturing system with starterpieces and a drive system. The touch probe can operate in threedimensions.

As discussed further below, the additive manufacturing system may beconfigured to print 3D items in a horizontal direction, a verticaldirection, or along other orientations (e.g., slopes relative to thehorizontal and vertical directions). In each of these embodiments, thelayers of a printed 3D item may be stabilized by one or more printedsupports or “scaffolds”, which brace the 3D item laterally relative tothe printing axis of the system to address forces parallel to the buildplane. The supports in horizontal printing act as a printed supportstructure.

In printing horizontally in a layer-by-layer manner from a print headnozzle, the layers of a 3D item being printed grow horizontally alongthe z-axis. As such, the “printing axis” in FIGS. 1-12 is a horizontalz-axis axis, and each layer extends parallel to a vertical x-y buildplane.

In this situation, the layers of 3D item are printed on layers ofsupport structure that extend from the starter pieces as describedherein, to support the item weight to the support rails also describedherein, which are correspondingly disposed on a platen.

For a horizontal printing operation, such as shown in FIGS. 1-12, theprinting z-axis is a horizontal axis, and each layer of the 3D item andits support structure extend along the vertical x-y build plane. Infurther alternative embodiments, the layers of 3D items, supportstructures, and scaffolds may be grown along any suitable axis.

Horizontal Printing

FIGS. 1-12 illustrate example additive manufacturing systems of thepresent disclosure having extended printing volumes for printing long 3Ditems horizontally, such as discussed above for a 3D item. FIGS. 1-5illustrate system 100, which is a first exemplary manufacturing systemfor printing or otherwise building 3D items, support structures, and/orscaffolds horizontally using a layer-based, additive manufacturingtechnique. Suitable systems for system 100 include extrusion-basedadditive manufacturing systems developed by Stratasys, Inc., EdenPrairie, Minn. under the trademark “FDM”, which are oriented such thatthe printing z-axis is a horizontal axis. In horizontal printing, theprint axis is parallel to the print plane, and movement is perpendicularto the print plane.

As shown in FIG. 1, system 100 may rest on a table or other suitablesurface 102, and includes chamber 104, platen 106, platen gantry 108,print head 110, head gantry 112, tool changer 113, and consumableassemblies 114. Chamber 104 is in one embodiment enclosed by chamberwalls, and initially contains platen 106 for printing 3D items, supportstructures, and/or scaffolds. Support structures and scaffolds aredescribed in further detail in co-pending application Publication No.2014/0052287.

In the shown embodiment, chamber 104 includes a heating mechanism, whichmay be any suitable mechanism configured to heat chamber 104, such asone or more heaters and air circulators to blow heated air throughoutchamber 104. Heating mechanism may heat and maintain chamber 104, atleast in the vicinity of print head 110, at one or more temperaturesthat are in a range between the solidification temperature and the creeprelaxation temperature of the item material and/or the support material.This reduces the rate at which the item and support materials solidifyafter being extruded and deposited (e.g., to reduce distortions andcurling), where the creep relaxation temperature of a material isproportional to its glass transition temperature. Examples of suitabletechniques for determining the creep relaxation temperatures of the itemand support materials are disclosed in Batchelder et al., U.S. Pat. No.5,866,058.

Chamber walls may be any suitable barrier to reduce the loss of theheated air from the build environment within chamber 104, and may alsothermally insulate chamber 104.

In some embodiments, system 100 may be configured to actively reduceheat loss through a port in the chamber 104, such as with an aircurtain, thereby improving energy conservation. Furthermore, system 100may also include one or more permeable barriers at the port, such asinsulating curtain strips, a cloth or flexible lining, bristles, and thelike, which restrict air flow out of the port, while allowing platen 106to pass therethrough.

In the shown example, print head 110 is a dual-tip extrusion headconfigured to receive consumable filaments or other materials fromconsumable assemblies 114 for printing a 3D item, support structure, andscaffold onto a receiving surface of platen 106. Examples of suitabledevices for print head 110 include those disclosed in Crump et al., U.S.Pat. No. 5,503,785; Swanson et al., U.S. Pat. No. 6,004,124; LaBossiere,et al., U.S. Pat. Nos. 7,384,255 and 7,604,470; Leavitt, U.S. Pat. No.7,625,200; Batchelder et al., U.S. Pat. No. 7,896,209; and Comb et al.,U.S. Pat. No. 8,153,182.

In additional embodiments, in which print head 110 is aninterchangeable, single-nozzle print head, a plurality of additionalprint heads 110 may be stored, for example within tool changer 113 asshown in FIG. 1, and may be interchangeably used for different printingfunctions. In one embodiment, tool changer 113 holds up to threeseparate print heads. Examples of suitable devices for each print head110, and the connections between print head 110 and head gantry 112include those disclosed in Swanson et al., U.S. Patent ApplicationPublication No. 2012/0164256.

Print head 110 is supported by head gantry 112, which is a gantryassembly configured to move print head 110 in (or substantially in) thex-y plane parallel to platen 106. While the additive manufacturingsystems discussed herein are illustrated as printing in a Cartesiancoordinate system, the systems may alternatively operate in a variety ofdifferent coordinate systems. For example, head gantry 112 may moveprint head 110 in a polar coordinate system, providing a cylindricalcoordinate system for system 100.

Suitable devices for consumable assemblies 114 include those disclosedin Swanson et al., U.S. Pat. No. 6,923,634; Comb et al., U.S. Pat. No.7,122,246; Taatjes et al, U.S. Pat. Nos. 7,938,351 and 7,938,356;Swanson, U.S. Patent Application Publication No. 2010/0283172; andMannella et al., U.S. patent application Ser. Nos. 13/334,910 and13/334,921.

Suitable materials and filaments for use with print head 110 includethose disclosed and listed in Crump et al., U.S. Pat. No. 5,503,785;Lombardi et al., U.S. Pat. Nos. 6,070,107 and 6,228,923; Priedeman etal., U.S. Pat. No. 6,790,403; Comb et al., U.S. Pat. No. 7,122,246;Batchelder, U.S. Patent Application Publication Nos. 2009/0263582,2011/0076496, 2011/0076495, 2011/0117268, 2011/0121476, and 2011/02331164; and Hopkins et al., U.S. Patent Application Publication No.2010/0096072. Examples of suitable average diameters for the filamentsrange from about 1.02 millimeters (about 0.040 inches) to about 3.0millimeters (about 0.120 inches). Further in some embodiments, pelletsof material are used as consumable feed stock. In such embodiments, aviscosity pump using a pellet-fed screw extruder may be used. Particlematerials are fed to or drawn by the viscosity pump from particlehoppers (e.g., consumable assemblies 114), and are heated and sheared toan extrudable state, and extruded from a nozzle of the viscosity pump,as described in greater detail in U.S. Patent Application PublicationNo. 2014/0048981 and U.S. Pat. No. 8,955,558.

System 100 also includes in one embodiment controller 116, which is oneor more control circuits configured to monitor and operate thecomponents of system 100. For example, one or more of the controlfunctions performed by controller 116 can be implemented in hardware,software, firmware, and the like, or a combination thereof. Controller116 may communicate with chamber 104 (including any heating mechanism),print head 110, motor (not shown), and various sensors, calibrationdevices, display devices, and/or user input devices over suitablecommunication lines.

In some embodiments, controller 116 may also communicate with one ormore of platen 106, platen gantry 108, head gantry 112, and any othersuitable component of system 100. While illustrated as a single signalline, communication lines may include one or more electrical, optical,and/or wireless signal lines, allowing controller 116 to communicatewith various components of system 100. Furthermore, while illustratedoutside of system 100, controller 116 and communication lines can beinternal components to system 100.

System 100 may also communicate with a computer 115 located with system100 or remote therefrom, which may be one or more computer-based systemsthat communicate with system 100 and/or controller 116, and may beseparate from system 100, or alternatively may be an internal componentof system 100. Computer 115 includes computer-based hardware, such asdata storage devices, processors, memory modules and the like forgenerating and storing tool path and related printing instructions. Thecomputer 115 may transmit these instructions to system 100 (e.g., tocontroller 116) to perform printing operations.

During operation, controller 116 may direct print head 110 toselectively draw successive segments of the item and support materialfilaments from consumable assemblies 114. Print head 110 thermally meltsthe successive segments of the received filaments such that they becomemolten flowable materials. The molten flowable materials are thenextruded and deposited from print head 110, along the printing z-axisaxis, onto the receiving surface for printing the 3D item (from the itemmaterial), support structure (from the support material), and scaffold(from the item and/or support materials).

Print head 110 may initially print one or more layers of supportstructure onto receiving surface to provide a base for the subsequentprinting. This maintains good adhesion between the layers of a 3D itemand a build sheet, and reduces or eliminates any tolerance to flatnessbetween the receiving surface of the platen 106 and the x-y plane.

After the support structure is initially printed, print head 110 maythen print layers of the 3D item and scaffold, and optionally anyadditional layers of support structure. The layers of support structureare intended to support the bottom surfaces of the 3D item along theprinting z-axis against curl forces, and any support layers are intendedto brace the 3D item against gravity along the vertical x-axis. Printingis performed in this embodiment in a Z-direction indicated by arrow 120.X-Y-Z orientation indications are provided in FIGS. 1-4.

As layers of the item are printed in the horizontal direction, the printhead 110 moves along print roads to build the item. In some embodiments,the print head 110 has enough variability in position to allow for theprinting of a number of layers (in one embodiment on the order of onehundred (100) layers) before movement of the item is performed. Printingmultiple layers without moving the item in one embodiment is performedbecause as the item is built, the weight of the item increases with eachlayer of the item built. On a system such as system 100, in which thelength/size of the item is undetermined and can be quite large, an itemcan weigh several hundred pounds or more. Indexing to an item of suchsize and weight is difficult since moving an item of such size andweight is not as precise as the resolution to which the item is beingprinted. Accuracy of movement of, for example, a print head such asprint head 110, is much higher. Therefore, accuracy of position of asmaller component can be much higher than accuracy in positioning thelarger item.

To ensure sufficient position accuracy, a touch probe 118 is used in oneembodiment to assist in registration for the printing of layers of anitem being printed. Touch probe 118 is in one embodiment a plunger thatis used to accurately determine a current Z-position so that a printingtip of a print head may be positioned to within a resolution on theorder of one tenth the resolution of the print head. For example, with aprinting resolution of on the order of 0.001-0.003 inches, the plunger118 determines a current Z-position of the item being printed to 0.0001inches, approximately ten times finer than the resolution of the printhead. As print operations are typically performed within a heatedchamber, thermal expansion of components such as the touch probe 118 canbe significant. With temperatures in the chamber 104 running on theorder of ˜350° F. (˜180° C.), thermal expansion on a component such astouch probe 118 could easily be on the order of 0.001 inches or more,rendering the resolution of the touch probe moot compared to the printresolution. In one embodiment, the touch probe components, especiallythe components that comprise the plunger portion of the touch probe, arespecialized materials with low coefficients of thermal expansion, suchas Invar®, a nickel-iron alloy. Further, as is described in furtherdetail below, the temperature of the touch probe is on one embodimentmaintained at or below about 212° F. (100° C.).

Movement of a large and/or heavy item is accomplished on one embodimentwith a plurality of rails and drivers, such as are shown and describedin further detail in FIGS. 2-8. Referring now to FIGS. 2-8, the gantry108 is described in greater detail. With items that are printedhorizontally, such as with a system 100 as described herein, a gantrysuch as gantry 108 is used to assist in supporting the item as it isprinted and moved to allow further printing by the print head 110.Components of the gantry 108 and platen 106 assist in moving the itemwhen it is desired to move the item.

As a horizontally oriented item may be much longer than the chamber ormachine which is printing it, the item is eventually moved beyond theheated chamber. In a horizontally printed item, embodiments of thepresent disclosure move the item on the gantry 108 in a directionperpendicular to the printing plane. The platen 106 may be removed andset aside when a part, such as elongated part 2902 shown in FIG. 24 isbeing printed with system 2900, to a length extending beyond the extentof the gantry 108. In one embodiment, after removal of the platen 106,the part 2902 is supported by a platform or table 2904 that is at thesame height as the gantry 108 but allows extension of the elongated part2902 beyond the gantry 108. The platform or table 2904 may be used toprovide support for a part 2902 having a length greater than the gantry108. The size of the table or platform 2904 may be selected dependingupon the length to which the part 2902 is to be printed. It should alsobe understood that additional tables or platforms 2904 may be used toextend the support for the elongated part 2902 even further, withoutdeparting from the scope of the disclosure. FIG. 24 shows a system 2900wherein a support table 2904 is used to support elongated part 2902 thatextends past the gantry 108. In this embodiment, platen 106 is removedand set aside, in one embodiment on a separate table 2906.

FIG. 25 is a close-up view of the system 2900 with the platen 106 in aposition in which it nears the end of the gantry 108. In thisembodiment, as the platen 106 to which the three-dimensional item 2902is secured approaches the end of the gantry 108, a limit switch system3000 is engaged to stop further advancement of the platen 106 on thegantry 108. Limit switch system 3000 in one embodiment comprises a block3002 secured to the platen 106, such as on a cross brace 3010 of theplaten 106. Block 3002 carries or is attached to a contact arm 3004 thatextends in one embodiment in an axis parallel to a direction of movementof the platen 106 on the gantry 108 away from the print head, asindicated by arrow 120. As the platen 106 approaches the end of thegantry 108, the contact arm contacts limit switch 3006, and the limitswitch system 3000 instructs a controller or computer (such ascontroller 116 or computer 115) to stop motion of the platen. Limitswitch system 3000 is shown as using a mechanical limit switch 3006. Itshould be understood that different types of switches, for exampleelectrical switches, electromagnetic switches, and the like, could beused with limit switch system 3000 without departing from the scope ofthe disclosure.

Once limit switch system 3000 halts motion of the platen 106 as it nearsthe end of the gantry 108, the three-dimensional item, which isreleasably secured to the platen 106, is released from the platen 106,the platen 106 is pulled away from the three-dimensional item, andremoved. In one embodiment, the platen 106 is removed to a separatetable such as table 2906 as shown in FIG. 24. Then, a support table,such as table 2904, is placed at the end of the gantry 108, and printingof the three-dimensional item continues without the platen 106. In thisembodiment, the starter piece or pieces (e.g., 900 and/or 1200), thatprovide a base for the building of the three-dimensional item asdescribed herein with respect to FIGS. 9-13, support thethree-dimensional item. In one embodiment, the print foundation isreleasably secured to the three-dimensional item, and the starter pieceor pieces support the three-dimensional item when the print foundationis released from the three-dimensional item. Releasing thethree-dimensional item from the print foundation (e.g., platen 106) isdone in one embodiment when the three-dimensional item is indexed tonear an end of the gantry 108.

While a platen 106 has been described herein in which a build sheet isfixed on the platen 106 or other component having a receiving surface,which may be a build sheet fixed on the platen 106 and held there with avacuum, it should be understood that other releasably securablemechanisms for holding the three-dimensional item to the platen areamenable with the embodiments of the removable platen as describedherein. By way of example only and not by limitation, such mechanismsinclude mechanical attachments (e.g., clamps, cams, or the like),magnetic attachments, electro-magnetic attachments, and the like.

As print resolutions become increasingly fine, a number of layers may beprinted on an item before it is moved on the gantry 108. In 3D printing,there is a significant amount of movement of a print head along roads,and between roads. With the amount of movement of the print head in aprinting operation, speed of movement of the print head, and also theprinted item, becomes a factor. The speed and accuracy with which asmaller, lighter print head may be moved is higher than the speed andaccuracy of movement of a large and heavy item. Moving a lighter weightcomponent such as the print head is faster than moving a heavier item,which is a consideration in any manufacturing process. In embodiments ofthe present disclosure, multiple layers of an item are printed beforeany movement of the item. In one embodiment, the number of layersprinted before moving the item is one hundred (100). All moves withinthe about one hundred (100) layers between movement of the item areperformed by movement of the print head. Once about one hundred (100)layers have been printed, the item is moved. Although about one hundred(100) layers is discussed between movement of the item, it should beunderstood that a larger or smaller number of layers may be printedbefore movement of the item, and that the number of layers between itemmovements may be variable and depend on any number of factors includingmanufacturing conditions, print materials, the geometry of the itemitself, and the like.

For example, in one embodiment, the horizontally printed item is movedon the gantry along a series of rails, using clamps and cylinders toadjust its position before the printing of additional layers of theitem. FIG. 2 illustrates generally a configuration of system 100including platen 106 and gantry 108. Platen 106 is movable along thegantry 108 in the direction of the Z-axis. Movement of the platen 106along gantry 108 is performed in one embodiment as shown in FIGS. 3-8.

FIG. 3 is a top view of the system 100, showing platen 106, gantry 108,a torque tube 302, torque tube cylinder 304, and a series of drivenrails 306, fixed rails 308, cylinders 304, 310, and clamps 305, 312,that work together in one embodiment to move an item being printed withsystem 100 along gantry 108. The clamps 305, 312 are in one embodimentlinear pneumatic clamps that are positioned within the rails such thatthe clamps may releasably engage a three-dimensional item being printedwith the system 100. Torque tube 302 is a tube or rod that is rotatablyconnected to the frame of the gantry 108, in one embodiment to edgerails 311 of the gantry 108, so as to be rotatable along an axisperpendicular to the edge rails 311. Torque tube cylinder 304 isconnected to torque tube 302 to drive the torque tube 302 rotatablytoward the cylinder 304 and rotatably away from the cylinder 304, whenthe cylinder 304 extends and retracts, respectively. The cylinder 304 issecured to the torque tube 302 with a mounting bracket or a pin. Torquetube is therefore rotatable between a first position in which it isrotated away from torque cylinder 304 and a second position in which itis rotated toward the torque cylinder 304, along a rotation indicationarrow 322 (FIG. 6).

Driven rails 306 are connected to the torque tube 302. Four driven rails306 are shown, although it should be understood that more or fewerdriven rails 306 may be used without departing from the scope of thedisclosure. Each driven rail 306 has a respective mounting bracket andclamp 312, and each clamp 312 is operable to secure a driven rail 306 tothe item being printed on the platen 106 to fix the item with respect tothe platen 106 and gantry 108, in one embodiment by inflation of abladder with air cylinder 310 that engages the clamp 312 along a lengthof the driven rail 306. When a clamp 312 is secured to an item beingprinted, the item being printed is also secured against relativemovement with the platen 106. The clamps in one embodiment are linearpneumatic clamps the extend along a length of an opening in theirrespective rail.

When it is desired to clamp an item being printed to the platen 106 witha driven rail 306, its air cylinder 310 engages the clamp 312. When theclamp 312 is engaged, the driven rail 306 and the item its clamp engagesis fixed against motion relative to the platen 106. Rotation of thetorque tube 302 toward the torque tube cylinder 304 when the drivenrails 306 are clamped to the item being printed, which is fixed to thebuild sheet of platen 106 on which it is being printed, moves the drivenrails 306 and therefore the platen 106 and its associated item towardthe cylinder 304. Rotation of the torque tube 302 away from the torquetube cylinder 304 when the driven rails 306 are clamped to item beingprinted moves the driven rails and therefore the platen 106 and itsassociated item away from the cylinder 304. In one embodiment, thetorque tube cylinder 304 extends and retracts approximately an inch,allowing for incremental motion of the driven rails 306, item beingprinted, and platen 106 by approximately the same amount when the drivenrails 306 are clamped to the item being printed.

It should be understood that incrementing the platen 106 on the gantrymay be in increments of greater than an inch by the use of a differenttorque tube cylinder length. In one embodiment, the coarse adjustment ofthe item is on the order of less than one inch to six inches. Further,the distance of the coarse adjustment does not need to be constant foreach incrementing move of the platen. That is, depending upon partgeometry and build parameters, the increment of motion of the platen 106may be made at any distance within the range of available motion of thetorque tube cylinder 304.

Indexing the part along with the platen 106, or after the platen 106 hasbeen removed, may also be done according to the size of a thermal zonein the build chamber of the system 100, 2400. The increment of motion ofthe platen 106, or the three-dimensional item after removal from theplaten 106, is chosen in one embodiment based on a size of the thermalzone within the build chamber that maintains a temperature of thethree-dimensional item within a desired temperature range. That is, aprint head (such as print head 110) may build up layers of athree-dimensional item within the desired thermal zone within the buildchamber to maintain three-dimensional item temperature within a desiredrange. Once the print head is outside of the desired thermal zone, thepart may be indexed along the gantry 108 or support table 2904 tomaintain the printing operation within the desired thermal zone.

While printing in layers has been discussed, it should be understoodthat printing of a three-dimensional item may be along a non-planar toolpath, such as a spiral or the like.

Fixed rails 308 are not connected to the torque tube 302, and thereforedo not move as the torque tube 302 is rotated. Each fixed rail 308 alsohas a mounting bracket and clamp 312 for securing the clamp, andtherefore the rail 308, to the item being printed in the same manner asdescribed above with respect to the fixed rails 306. Fixed rail 308clamps 312 are engaged during an item building operation. A center fixedrail, 308 c, serves in one embodiment as an alignment rail. Thealignment rail is used in one embodiment to align an item on the platen106 and gantry 108, as is discussed in greater detail below.

Sequential clamping of clamps 312 and movement of the driven rails 306allows the movement of an item along the gantry 108 as follows. Duringan item building operation, that is, when layers are being printed tothe item, all clamps 312 of rails 306 and 308 are clamped against motionof the item being printed and therefore the platen 106 relative togantry 108. To move the platen 106 and therefore an item away from theprint head along the gantry, that is, toward an end 320 of the gantry108 distal to the print head and initial position of platen 106, theclamps 312 of the fixed rails 308 are released. The driven rails 306remain clamped. The torque tube cylinder 304 is retracted so that thedriven rails 306, the platen 106, and the item being built move towardthe torque tube cylinder 304 and the second position. In this manner,the item is moved toward the distal end 320 of the gantry 108. When themovement is complete, the clamps of the fixed rails 308 are clamped, andthe clamps of the driven rails 306 are released. The torque tubecylinder 304 rotates the torque tube 302 away from the cylinder 304 tothe first position, moving the driven rails 306 back to their firstpositions while the platen 106 and therefore the item being printed donot move. All clamps of rails 306, 308 are again clamped for a buildoperation, and the process repeats as necessary for moving the item onthe gantry 108. The process allows for movement of the platen 106 andthe item being built along the gantry to whatever position is desired.

In one embodiment, each clamp 312 comprises a pneumatic clamp that isengaged when a silicon bladder positioned within a slot of its rail isinflated by its respective air cylinder 310. Alternatively, eachmounting bracket could be engaged when its silicon bladder is deflated.Further, it should be understood that although pneumatic clamps aredisclosed, other clamps or mounting brackets suitable for engaging anddisengaging the rails 306 and 308 are suitable for use with the variousembodiments, such as electric clamps, mechanical clamps, andcombinations thereof, and are within the scope of the disclosure and ofone skilled in the art.

In one embodiment, each of the rails other than the center rail 308 chas two movable edge portions, so that the rails float in the Xdirection. Center rail 308 c comprises one fixed edge portion, and onemovable edge portion. Therefore, the position of the fixed edge portionof center rail 308 c is known and unchanging, so that the center rail308 c is fixed in the X direction.

FIGS. 4-5 show closer views of the portion of the gantry 108 where therails 306 and 308 interact with the torque tube 302 and torque cylinder304.

FIG. 6 is a perspective view of the torque tube 302, torque tubecylinder 304, and rails 306 and 308 of the gantry 108 without othercomponents shown, to more clearly show their arrangement. The torquetube is rotatable as shown by arrow 322 to allow for the movement of thedriven rails 306 forward and back between their first and secondpositions with the extension and/or retraction of the torque tubecylinder 304.

FIGS. 7 and 8 are perspective views of the platen 106 and center fixedrail 308 c (FIG. 7) and the platen 106 on gantry 108 (FIG. 8). As isseen in FIGS. 7-8, a guide portion 702 of platen 106 is connected to aT-shaped member 704. T-shaped member 704 has a substantially verticalportion that moves within slot 706 of center fixed rail 308 c, which isused in this embodiment as an alignment rail. An item being printed isguided along the gantry 108 through the interaction between the T-shapedmember 704, the guide slot 706, and the clamps 312 of the gantry 108.T-shaped member 704 functions in one embodiment as a center alignmentkeel, and in one embodiment, it extends from a front portion of theguide portion toward the front part of the platen 106, near to where astarter piece (such as starter pieces 900 and 1200 described furtherbelow) is used. The center alignment keel allows for centering of theplaten 106 on the gantry 108. Travel limit sensors 710 are used in oneembodiment to limit the movement of the platen 106 so that it does nottravel outside of defined position limits. Platen 106 further hassupport pads 714 at its front and its rear, which serve to support theplaten 106 on the gantry 108 (shown and described in further detail withrespect to FIGS. 14-16 below). When a clamp 312 for a rail 306 or 308engages, the keel for that particular rail is clamped to its rail sothat it cannot move except with movement of the rail. Therefore, in themotion of the driven and non-driven rails is made, the movement of theclamped rails also moves the platen 106, and consequently, an item thatis being printed.

In building very long parts or parts in segments, new layer alignment inthe X-Y plane may become problematic. Small misalignments can lead tolarger overall errors as part length increases. Alignment of a new layerto a previously printed layer is performed in smaller systems with acontinuous Z motion mechanism that provides proper tolerances. Once apart gets larger, continuous Z motion mechanisms that are longer thanthe entire part are difficult to build, and can become unwieldy. In oneembodiment, at the boundary of the Z axis, a separate mechanism is usedto move the part to allow the Z axis to recover its length and tocontinue building the part. These functions are discussed herein aslocal Z and the Z drive respectively.

The Z drive operates in various embodiments as described herein. The Zdrive allows for movement of a part in a Z direction. Once a part hasbeen shifted in the Z direction by the Z drive, alignment in the X-Yplane may not be accurate. In order to continue properly aligned partbuilding, registration in the Z direction is performed, such as by usingthe touch probe as discussed herein, and registration in the X-Y planeis performed as follows. Once the Z registration is performed, the partlocation in Z is known. To register the part correctly in the X-Y plane,in one embodiment, an X-Y fiducial is used.

Such a fiducial may be part-based, that is, on the part being printed,or may alternatively be in a support structure. While the fiducial maybe formed from support material or from part material, when the fiducialis formed from part material, the fiducial behaves in the same way thatthe part does during cooling, such as but not limited to the amount andtiming of sag, and the like. That is, when the fiducial is formed out ofthe same material as the part, the fiducial behaves similarly to thepart in the build chamber (e.g., if the part sags, the fiducial alsosags.

Use of a fiducial, either part-based or support-based, provides a methodfor determining the XY alignment and the Z displacement. In oneembodiment, a fiducial comprises a specific part geometry that isconstructed along with the target geometry. A measurement system capableof measuring the embedded fiducial geometry determines X-Y alignment. Inone embodiment, the part geometry of the fiducial comprises a rightangle of material constructed at a known location relative to the targetgeometry. One or more fiducials may be constructed on each layer of thepart.

A single fiducial on a part is shown in FIG. 17. FIG. 17 shows a part2202 with a single fiducial 2204. The fiducial 2204 is constructed in amanner that allows a measurement system (such as the touch probe 118) toproperly determine the location of the fiducial in X and Y. Fiducial2204 is shown in closer detail in FIG. 18. Fiducial 2204 comprises inthis embodiment a known X-Y offset point 2206, an X reference edge 2208extending from the known offset point 2206, and a Y reference edge 2210extending orthogonal to the X reference edge from the known offset point2206. The known offset point 2206 is the vertex of a right angle havingsides 2208 and 2210. As shown, the fiducial 2204 is on a part 2202.However, when the part being printed uses support structures, a fiducialor fiducials may alternatively be built into the support structurewithout departing from the scope of the disclosure.

Just prior to displacing the part in Z with the Z drive, the system inone embodiment measures the Z location, such as with the touch probedescribed herein, and measures a location of the fiducial to get a knownX-Y location before movement of the part. Once the part is displaced,the Z location of the part and the X-Y location of the fiducial aredetermined again, providing a new location in X, Y, and Z. The newlocation of the fiducial is compared to the previous location of thefiducial, or to the planned part location. The new Z location iscompared to the previous Z location. This information allows the systemto compensate on the fly for the Z displacement as well as X-Yalignment. In another embodiment, use of more than one fiducial may beused to compensate for XY rotation, and for shifts in the Z plane.

In operation, a method for determining an X, Y, and Z position comprisesdetermining a Z position as described herein, and determining an X and aY position as follows. A measurement system determines the location ofthe Y reference edge 2210 by moving an element, such as a probe, tocontact the Y reference edge 2210, giving the Y location. Themeasurement system determines the location of the X reference edge 2208by moving the element to contact the X reference edge 2208, giving the Xlocation. Once the X and Y locations of the reference edges 2208 and2210 are known, the offset point 2206 is known, and a precise locationin X-Y is also known. Coupled with the determined Z position, theposition of the part in X, Y, and Z is known to the precision of theprobe. In one embodiment, a measurement system used for determining Xand Y positions uses on the order of 0.25 inches of clearance with X andY reference edges of at least 0.02 inches long. As measurement elementscontinue to improve, clearance and length of reference edges may changewithout departing from the scope of the disclosure.

Embodiments of the present disclosure are capable of printing multiplelayers of a part before movement of the part is effected by the system100 as described herein. While X, Y, and Z position can be determinedafter each layer, in one embodiment, multiple payers are printed beforeX, Y, and Z positions are determined. In one embodiment, before thesystem 100 moves the part after a number of layers have been printed,the X, Y, and Z positions are determined as described herein. Followingmovement of the part in the Z direction, another determination of the X,Y, and Z positions is made for registration of subsequent layers on thepart.

A fiducial, such as fiducial 2204, is generated in one embodiment usinga digital file built with the fiducial appropriately configured in thedigital file. Given part geometry, an element of the actual part may besuitable for use as a fiducial without any modification. This couldoccur, for example, where the part has a defined right angle edge thatis properly aligned with the build platform. In this embodiment, thefeature structure of the part may be used as a fiducial. In otherembodiments, a fiducial is built into support structure for the part.Creating a fiducial comprises in one embodiment generating a digitalfile containing a fiducial, and building a part with the file. A filefor building a part in this manner contains structure therein with aknown substantially horizontal and a known substantially verticalcomponent that is capable of being used as a fiducial.

A method 2400 of building a three-dimensional item in an additivemanufacturing system is illustrated in flow chart form in FIG. 19.Method 2400 comprises printing a support structure for thethree-dimensional item in a layer by layer manner along the printingaxis in block 2402, and printing a layer of the three-dimensional itemwhile supporting the three-dimensional item laterally relative to theprinting plane with the support structure while printing thethree-dimensional item in block 2404. Building the part furthercomprises printing a fiducial structure having a known substantiallyvertical and a known substantially horizontal component. Printing thethree-dimensional item in a layer-by-layer manner is performed in oneembodiment along a horizontal printing axis parallel to a build plane inthe additive manufacturing system. Printing the fiducial structurecomprises printing the fiducial structure in the support structure inone embodiment, or as a portion of the three-dimensional item in anotherembodiment.

Method 2400 may further comprise printing a plurality of layers of thethree-dimensional item, including the fiducial structure in block 2406,determining a Z position of the three-dimensional item in block 2408,determining an X and Y position of the three-dimensional item using thefiducial structure in block 2410, moving the three-dimensional itemalong the horizontal printing axis in block 2412, determining a new Zposition of the three-dimensional item in block 2414, determining new Xand Y positions of the three-dimensional item using the fiducialstructure in block 2416, and printing another plurality of layers of thethree-dimensional item in block 2418. The printing of another pluralityof layers uses the new positions of X, Y, and Z to register the anotherplurality of layers to the previously printed layers. In one embodiment,determining an X and a Y position for the three-dimensional itemcomprises moving the touch probe vertically to contact a knownsubstantially horizontal edge of the fiducial to determine the Xposition, and moving the touch probe horizontally to contact a knownsubstantially vertical edge of the fiducial to determine Y position.

In additive manufacturing systems, a byproduct of printing is wastematerial that can build up on a print head or tip, material extrudedfrom a print head to expend one material to be replaced by another,material that has been stored for a period of time in a print head thathas degraded, and the like. The process of additive manufacturing usesautomated cleaning maintenance and priming of the modeling tool forquality printing and for accurate auto calibration of the modeling tool.For example. in additive manufacturing, multiple tools may be swapped inand out during the part build to alter materials, colors, and tool tipsof varying geometries. As the tool tip location varies slightly due totolerances the tip position is learned so its position can be alignedwith the prior tool's tip location. Contamination or buildup on themodeling tip may compromise the accuracy of the homing calibrationprocess. Further, prior to being swapped in, the modeling tool may havebeen stored for a period of time. The material resident in the tool issubject to degradation and may be purged and refreshed with new materialin order to prevent part quality issues.

In one embodiment, a waste purge system removes purged waste materialfrom the tool service location to a waste location. Conventionaldisposal processes are oriented vertically where gravity can be used fortransport of the waste material. In embodiments of the presentdisclosure which use a vertical print plane and horizontal printing, aseparate system is used to transport waste material horizontally. In oneembodiment, a high volume vacuum is used to collect and transportmaterial that is discharged from a modeling tool oriented horizontally.This method may also be utilized to enhance the efficiency and speed ofa conventional vertical modeling tool.

As illustrated in FIGS. 20, 21, 22, and 23, the modeling tool traversesin a vertical XY plane to build a part that grows in the Z direction.The purged material is transported in the horizontal Z direction aswell. FIG. 20 shows an isometric view of a vacuum purge system 2502along with a modeling device 2501, and waste bin 2503. Purge system 2502includes tip sensing apparatus 2504 and 2505, and tip cleaner 2506. Tipcleaner 2506 is used to scrub any residual material from the modelingtip before tip sensing apparatus 2504 and 2505 sense the tip location. Atip cleaner such as tip cleaner 2506 is disclosed in further detail inU.S. Pat. Nos. 6,722,872 and 7,744,364, which are commonly owned by theassignee of the present disclosure. Sensor 2505 is in one embodiment anopen close contact that detects the tip location in the Z direction, andsensor 2504 is in one embodiment a camera to detect the tip location inthe X Y directions. Sensor 2504 is surrounded in one embodiment by alight array 2507 to better illuminate the tip for the camera. FIG. 20shows the model tool in a purge position, FIG. 21 shows the model toolin a Z detection position, and FIG. 22 shows the model tool in an XYmeasuring position. Items 2516 are structural members used to locate andsupport the purge components.

FIG. 23 shows a close-up perspective view of a portion of the purgesystem 2502 in greater detail. Purge system 2502 further comprises avacuum generator 2508 (such as, for example only, a model ZH10-X185available from SMC Corporation), a tube fitting 2509 to which a plastictube 2510 is attached, and to which air of sufficient pressure and flowis provided to enable vacuum generator 2508 to produce a vacuum intotube 2512. Tube 2512 is, in one embodiment, a tube with suitable insidegeometry to draw in without obstruction purged material from a modelertool (such as tool 2501). Tube 2512 may use tapered geometry to allow aless precise location of the modeling tip. Alternatively, tube 2512 maybe reduced in diameter to increase air velocity to better draw in thepurge, or configured in other ways that will be apparent to those ofskill in the art to benefit the purge process.

An unobstructed low friction straight tube 2513 directs the purgematerial to an external waste container 2503 (see FIGS. 20-22). Coupling2514 couples tubes 2512 and 2513 and in one embodiment, has a smallangle to redirect the purge material to the straight tube 2513, anddeflector 2515 is also angled so as to direct the purged material intowaste bin 2503 without creating an obstruction to block purge material.It should be understood that the angles of such tubes and couplings maybe modified without departing from the scope of the disclosure.

Starter Pieces

Referring now to FIGS. 9-13, views of starter pieces (e.g., starterkeels) 900 (FIGS. 9-11) and 1200 (FIGS. 12-13) are shown. The starterpieces fit under the platen 106 and above the rails of the gantry 108 toprovide a base for the building of the item. FIG. 9 show starter piece900 in perspective. Starter piece 900 is a center starter piece, andcomprises a main body 910 comprising a face surface, a keel 902 coupledto the main body 910 and including keel body 904 and guide tab 906, andat least one retaining mechanism 908. Keel face surface 910 has athickness 912. The thickness 912 is chosen in one embodiment to allow anabutting match of thickness between the main body 910 and a build sheetmounted to the platen 106, so that at a start of a build operation foran item, front edge 914 aligns with the build sheet to form a smoothtransition therebetween. Keel body 904 has a width 916. This widthallows the keel body to align with center guide rail (e.g., center rail308 c) of gantry 108 to assist in alignment of the item on the gantry108. The width 916 of keel body 904 allows the center starter piece 900to be fixed with respect to x-axis movement.

Guide tab 906 fits into a slot (not shown) in center rail (e.g., centerrail 308 c) to assist in fixing the starter piece 900 with respect toy-axis movement. The engagement of guide tab 906 with the slot in therail helps the item to not float in the Y-direction.

Starter piece 1200 is a non-center starter piece, is shown in FIGS.12-13, and comprises a main body 910 comprising a face surface, a keel1202 coupled to the main body 910 and including keel body 1204 and guidetab 1206. At least one retaining mechanism 908, main body 910, and keelfront edge 914 are identical to those parts of keel 900. Main body 910of starter piece 1200 has a thickness 912 the same as main body 910 ofkeel 900. Keel body 1204 has a width 1216 which allows the keel body1204 to align with guide rails 308 that are not a center guide rail (308c) of gantry 108. The width 1216 of keel body 1204 allows the starterpiece 1200 to float with respect to x-axis movement.

FIG. 14 shows a close-up perspective view of a portion of the platen106, starter pieces 900 and 1200, and their interactions with the rails306/308 of the gantry 108. Parts have been removed to show more clearlythe positioning and interaction between the parts. Specifically, thearea marked as area 1402 has had the platen face panel removed; the areamarked as area 1404 has had the platen face panel, support structure forthe platen panel, and a starter piece 1200 removed; the area marked asarea 1406 has had the platen face panel, support structure for theplaten panel, and a portion of the rail 308 c removed; and the areamarked as area 1408 has had the platen face panel, support structure forthe platen panel, a portion of the rail 306, and a starter piece 1200removed. The various views allow the showing of the engagement ofstarter pieces such as keels 900 and 1200 with rails such as rails 306and 308.

Keels 900 and 1200 as shown in areas 1406 and 1402, respectively, haveprotrusions 918 that comprise in one embodiment the at least oneretaining mechanism 908. The protrusions 918 engage openings 1412 in theplaten 106. Gaps 1412 are better seen without a starter piece in area1404. The double protrusions 918 allow a starter piece to be snappedinto the gap, and further, provide a protection against torque twistingof the starter pieces during item production. Because there are twoindependent protrusions 918, vibrations and torsions of the platen 106and the starter piece mounting area are dampened, so that the movementis not imparted to the starter piece main bodies 910, to help maintaincontinuity in the build process, and improves the quality of items beingbuilt. Since the starter pieces 900 and 1200 do not bend with movementof the structure into which they are snapped, build quality is improvedallowing for items to be built with increasingly tight tolerances. Whenitems are manufactured with tight tolerances, any variation due tomachine part vibration or the like can be imparted to the item. Thedouble protrusions 918 assist in reducing such a transfer of vibrationfrom the apparatus to the item.

In building an item on the starter pieces and the build sheet, thegeometry of the starter pieces is extended during the build operation toprovide a platform to support the item during the build operation. Thestarter piece geometry is extended for the length of the build,providing support for the item during the build operation.

Referring now to FIG. 15, a view similar to that of FIG. 14 is shown,but with the components of the apparatus 100 shown again. Platen 106 isshown with its positioning directly above starter pieces 900 and 1200.In one embodiment, one center starter piece 900 is used, and eightnon-center starter pieces 1200 are used, with four starter pieces 1200on each side of center starter piece 900. It should be understood thatmore or fewer starter pieces 1200 may be used without departing from thescope of the disclosure, and depending upon the size of the item to bebuilt. Each starter piece is associated with one of a driven rail 306 ora fixed rail 308. Driven rails and fixed rails in one embodimentalternate in the x-direction on the gantry 108. Center starter piece 900is placed at center rail 308 c in one embodiment. In one embodiment,support rails 1410 are placed between driven rails and fixed rails sothat no more than about 12 inches separates consecutive support rails1410. As can be seen, support rails 1410 alternate with driven and fixedrails 306 and 308, so that there is y-direction support for a built itemon the order of every six inches horizontally.

Referring now to FIG. 16, a close-up view of a portion of FIG. 15 isshown. FIG. 16 shows center starter piece 900 in place on center rail308 c, including keel 902 engaging slot 706 of center rail 308 c, andguide tab 906 engaging horizontal slot 1602 in slot 706. Similarly, eachstarter piece 1200 has its keel 1206 engaging slot 708 of its respectivedriven or fixed rail 306 or 308, and its guide tab 1206 engaginghorizontal guide tab slot 1604 in slot 708. Support pads 714 of platen106 rest on support rails 1410. It is on these support rails 1410, undersupport pads 714, that the platen 106 slides during movement of theplaten on the gantry. The support pads convey the weight of the platen106 and item to the support rails 1410, and then to the ground.

The support rails 1410 sit at a location below a bottom of the itembeing printed. The starter pieces 900 and 1200 are used as a base fromwhich to print down to form supports for the item being printed thatextend to the support rails. As the platen 106 moves on the gantry 108,the item being printed transfers some of its weight to the platen, andsome of the weight caused by the moment as the item extends away fromthe platen 106, to the support rails 1410 through the extended supportformed from the starter pieces. Further, the geometry of each starterpiece is replicated in the z-direction as well, to allow the platen 106to be secured with mounting brackets 312 by their engagement with theextended geometry of the starter pieces within the slots of the rails306 and 308 as the item is printed.

The keels 902 and 1202, and guide tabs 906, 1206, of starter pieces 900,1200 engage slots in rails 306, 308 of the gantry. The keels 902, 1202restrain movement of the starter pieces in an x-direction (as thex-direction is shown in the FIGS.) Specifically, keel 902 is nearly aswide as the width of its associated slot in center rail 308 c, andserves as an alignment keel to restrict movement of the starter piece,and therefore of the platen and item being printed, in the x-direction.The keels 1202 of starter pieces 1200 are narrower than their associatedslots in driven or fixed rails 306, 308, and float in the x-direction toallow the wider keel 902 in the center rail 308 c to be the alignmentkeel for the platen 106 and the item being printed. Horizontallyextending guide tabs 906 and 1206 engage horizontal channels extendingfrom the slots in their respective rails, and restrict motion of thestarter pieces, and therefore the platen and item being printed, in ay-direction (as the y-direction is shown in the FIGS.) Referring also toFIG. 16, the guide tab 906 engages channel 1602 in slot 706 of guiderail 308 c, and guide tabs 1206 engage channels 1604 in slots 708 ofremaining rails 306, 308, to prevent the starter pieces 900, 1200, theplaten 106, and the printed item from moving in the y-direction.

In printing an item using embodiments of the system described herein,the print head initially prints multiple layers of a support structureon a starter piece during printing of the item itself, the supportstructure being printed layer-by-layer as described herein. The layersof the support structure are in one embodiment printed with increasingcross-sectional area in the vertical x-y plane to extend, at an angle ofapproximately 45 degrees in one embodiment, toward the support rails1410 to ultimately provide support for the item by the support rails1410 and not the starter pieces 900, 1200 or platen 106. This layeringbuild-up is in one embodiment continued until the footprintcross-sectional area of the intended 3D item and support to the supportrails 1410 is reached. At that point, the support rails 1410 support theweight of the item, relieving pressure on the item itself and thestarter pieces 900, 1200. The geometry of the starter pieces 900, 1200is printed and maintained along the length of the item in oneembodiment, to allow for continued control of movement of the platen 106and therefore the item with respect to the gantry 108.

In one embodiment, after approximately 100 layers of support structureand an item are printed, the item and its support structure are moved asdescribed herein. As the item is moved as described herein, the item andits associated structure is moved in the direction of arrow 120 (FIG.1), and the support structure slidably engages the support rails 1410,which support the weight of the item through the support structureformed extending from the starter pieces. This allows the supportstructure to rest on and slide across the top surface of support rails1410 while platen 106 is indexed in the direction of arrow 120.

Removal of the item from the printed support and starter pieces afterthe piece is completed may be performed in various ways as is known inthe art. The printing and indexing apparatus and methods describedherein are amenable to use with various removal methods and structures.

Touch Probe

A touch probe 118 such as that discussed above is shown in greaterdetail in co-pending U.S. Patent Application Ser. No. 62/248,994,entitled “PROBE AND PRINTING METHODS FOR ADDITIVE MANUFACTURING SYSTEM”.

In operation, the touch probe 118 is used to register the location ofthe platen at an initial item build, and is used to register thelocation in the z-axis of the item being built as it is being built, orany portion of the item as it is being built. With the resolution of thetouch probe 118 being smaller than the resolution of the print headprinting, the location of the item, platen, build sheet, or the like isdetermined by the touch probe 118 with an accuracy that is more finethan the resolution of the print head. Registration operation in oneembodiment includes moving the touch probe 118 so that probe end 1704comes into contact with the platen or part to be indexed in theZ-direction. Once the probe end contacts the platen or part, a roughZ-position is known. The touch probe backs away from the platen or part,and at a slower speed, and knowing the rough location of the platen orpart, refines the Z-position by once again moving into contact with thepart or platen. This coarse-fine indexing allows for a more accurateZ-position determination.

In another embodiment, X-Y indexing of the system is also performed withthe touch probe 118. Each touch probe 118 has its own configuration ofthe tip end (e.g., tip end 1704). An imaging device, such as a camera,is used to capture an image of the tip end along a longitudinal axis ofthe touch probe 118. The tip center is located in the image, and the X-Ypositioning of the touch probe is enhanced. For each new tool that isloaded with the tool changer, a new image of the tip end is taken, astips have different centers and configurations.

In one embodiment, the plunger portion 1701 of touch probe 118 thatextends into a heated chamber (such as chamber 104) is constructed atleast in part from a material or materials that have a low coefficientof thermal expansion, to further control to a temperature for thecomponents of plunger 1701 which further limits thermal expansionthereof in a heated work environment, as described above. In oneembodiment, a low coefficient of thermal expansion material includesceramic.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the disclosure.

The invention claimed is:
 1. A layerwise method for printing athree-dimensional item with an additive manufacturing system, the methodcomprising: printing a first plurality of layers of thethree-dimensional item by depositing material from a print head onto aprint foundation of the additive manufacturing system by incrementing aposition of the print head tip in a first direction along a printingaxis and relative to the print foundation after each layer of the firstplurality of layers is printed; indexing the print foundation carryingthe printed layers in a second direction along the print axis, whereinthe second direction is opposite the first direction, and away from theprint head a distance of a second plurality of layers along the printingaxis after the first plurality of layers are printed, using a drivemechanism; moving the print head in the second direction, such that theprint head tip is proximate a last printed layer; printing a secondplurality of layers onto the first plurality of layers by incrementingthe position of the print head tip in the first direction along aprinting axis and relative to the print foundation after each layer ofthe second plurality of layers is printed; and repeating printing,incrementing, indexing and moving steps to build the three-dimensionalitem.
 2. The method of claim 1, wherein the drive mechanism comprises arail system comprising a plurality of driven rails and a plurality offixed rails, and wherein indexing the print foundation along theprinting axis comprises moving the driven rails with respect to thefixed rails while engaging the driven rails with the print foundation.3. The method of claim 1, wherein the printing axis is a horizontalaxis.
 4. The method of claim 2, wherein moving the driven rails withrespect to the fixed rails further comprises: disengaging clamps withinfixed rails of the system; engaging clamps within driven rails of thesystem; moving the driven rails from a first position to a secondposition with a torque cylinder and torque tube, the torque tube coupledto the driven rails; engaging the clamps within the fixed rails;disengaging the clamps within the driven rails; and moving the drivenrails from the second position to the first position with the torquecylinder and the torque tube.
 5. The method of claim 4, and furthercomprising printing a plurality of layers of a support structure for thethree-dimensional item onto the print foundation.
 6. The method of claim4, and further comprising probing the printed layers of thethree-dimensional item and/or the support structure after performing theindexing step, to verify accurate positioning of the print head relativeto the printed layers prior to printing additional layers.
 7. The methodof claim 2, wherein the drive mechanism further comprises a plurality ofsupport rails, and wherein printing comprises printing athree-dimensional item having a length greater than a length of thesupport rails.
 8. The method of claim 4, wherein engaging the clampscomprises engaging with the drive rails a starter piece affixed to theprint foundation.
 9. The method of claim 8, wherein disengaging theclamps comprises disengaging the drive rails from the starter piece. 10.The method of claim 3, and further comprising purging the print head ata purging location.
 11. The method of claim 10, wherein purgingcomprises discharging waste material from the print head substantiallyhorizontally and removing purged waste material from the purginglocation to a waste location using a vacuum to collect and transportmaterial discharged from the print head.
 12. A method for printing athree-dimensional structure comprising one or more parts and one or moresupport structures with an extrusion-based additive manufacturingsystem, the method comprising: printing one or more layers of thethree-dimensional structure by extruding material from a print head ontoa print foundation of the additive manufacturing system; incrementing aposition of the print head tip in a first direction along a print axisand relative to the print foundation after each successive layer isprinted until a first plurality of layers is printed; indexing the printfoundation carrying the printed layers in a second direction along theprint axis, the second direction being opposite the first direction, andaway from the print head a distance of a second plurality of layersafter the first plurality of layers are printed, using a drivemechanism; determining a location of a last printed layer of the firstselected plurality of layers; moving the print head along the printingaxis in the second direction based upon the determined location of thelast printed layer such that the print head tip is positioned to print anext layer onto the last printed layer; printing the next plurality oflayers by incrementing the position of the print head tip along a printaxis in the first direction and relative to the print foundation aftereach successive layer is printed until the second plurality of layers isprinted; and repeating incrementing, determining, indexing, moving andprinting steps to build the three-dimensional item.
 13. The method ofclaim 12, wherein the drive mechanism comprises a rail system comprisinga plurality of driven rails and a plurality of fixed rails, and whereinindexing the print foundation along the printing axis comprises movingthe driven rails with respect to the fixed rails while engaging thedriven rails with the print foundation.
 14. The method of claim 12,wherein the printing axis is a substantially horizontal axis.
 15. Themethod of claim 13, wherein moving the driven rails with respect to thefixed rails further comprises: disengaging clamps within fixed rails ofthe system; engaging clamps within driven rails of the system; movingthe driven rails from a first position to a second position with atorque cylinder and torque tube, the torque tube coupled to the drivenrails; engaging the clamps within the fixed rails; disengaging theclamps within the driven rails; and moving the driven rails from thesecond position to the first position with the torque cylinder and thetorque tube.
 16. The method of claim 12, and wherein determining theposition of the last printed layer comprises probing the printed layersof the three-dimensional structure in the X, Y and Z directions.
 17. Themethod of claim 13, wherein the drive mechanism further comprises aplurality of support rails, and wherein printing comprises printing thethree-dimensional structure having a length greater than a length of thesupport rails.
 18. The method of claim 15, wherein engaging the clampscomprises engaging with the drive rails a starter piece affixed to theprint foundation.
 19. The method of claim 18, wherein disengaging theclamps comprises disengaging the drive rails from the starter piece. 20.The method of claim 12, and further comprising purging the print head ata purging location.